This invention relates to plugs for embolization of a biological vessel and, more particularly, to biodegradable collagen plugs which may be placed inside a blood vessel for occlusion.
There is a great variety of clinical situations where blood vessels must be blocked, such as when bleeding in the brain needs to be controlled or when the blood supply to tumorous tissues must be blocked. Other examples of situations requiring permanent or temporary embolization include, but are not limited to, occlusion of saphenous vein side branches in a saphenous bypass graft procedure, neurovascular occlusion, chemoembolization, aortic aneurysm correction procedure, chronic venous insufficiency treatment, and renal embolization.
Various means have been used in these applications to occlude blood vessels, such as by advancing a small diameter catheter from a distant vessel, inflating a small rubber balloon at the end of the catheter to mechanically wedge it into place in order to block the vessel, and thereafter withdrawing the catheter. A disadvantage of this method is that the rubber balloon may become dislodged at a later time and become life-threatening as a free-floating embolus. Another procedure is to inject at the desired site in the blood vessel a suspension of collagen with clotting factors, thereby inducing an embolus. The clots will be re-absorbed with time, alleviating the risk of a free-floating embolus. This procedure, however, is not desirable when precise location of the embolus is desired because the clotting must be induced sufficiently rapidly such that the clot can be prevented from moving downstream to an undesired location or from forming microemboli before attaching to the blood vessel walls. Still another procedure, which has been suggested, is to use a syringe to inject through a catheter a liquid suspension of Gelfoam (registered trademark of Upjohn) particles or small "piedgets". While Gelfoam, manufactured from animal gelatin, has a sponge-like consistency when wet, the use of a syringe to inject suspended particles into a catheter limits the compression of the particles and the resultant mechanical fixation in-situ of the embolizing material.
It is therefore an object of the present invention to provide an occluding material (hereinafter broadly referred to as a plug) for creating a rapidly clotting, mechanically stable, bioresorbable embolus in a controlled vascular embolization process.
It is another object of the present invention to provide such a plug that can create such an embolus at a predetermined location within a blood vessel such as a branch from the saphenous vein.
It is still another object of the present invention to provide such a plug that can also deliver various active agents such as antibiotics to a specified site inside such a vessel.
Thus, the issues which are critical to the plug design include chemical, mechanical and biological interactions of the material with the vein and blood. In certain applications, it may be desirable that the plug material can occlude a flow permanently, and be replaced by native tissue. In other applications such as chemoembolization of the hepatic artery, on the other hand, temporary occlusion may be preferred, allowing the material to erode gradually and normal flow restored in the vessel. It is therefore still another object of the present invention to provide a plug made from a material of which the rate of bioerosion can be controlled.